This invention relates to a system of, apparatus for, and a method of constructing a shoring structure of interlocking sheet piling members which are to be driven into the ground, and, more specifically, to such a system, apparatus or method for positioning the interlocking piling members forming the walls of a cofferdam cell or other shoring structure. Still further, this invention relates to a guide for aiding in the threading of the interlocking sheet piling members.
Conventionally, a shoring structure, such as a cofferdam as may be used in the construction of bridge supports or dams, may utilize a series of circular or polygonal cells adjacent to or interconnected to one another. The cells are each formed by elongate sheet piling members having interlocking connections at their side edges with the sheet piling members driven into the earth to a considerable depth. A circular template may be initially positioned at a desired location for locating the cofferdam cell and for holding and guiding the sheet piling members as they are driven to form the circular cofferdam shell. The template is positioned on the interior of the cell to be formed and the piling members are aligned and guided by the template to maintain the cofferdam in a desired circular cross-section and of a desired dimension. Typically, a first piling member is positioned vertically against the template and is partially driven into the ground by a suitable pile driving apparatus. This partial driving of a sheet piling member is oftentimes referred to as "tacking". Then, a next sheet piling member is hoisted by a crane or other lifting apparatus so that the next piling member extends vertically and so that the bottom end of the next piling member is lifted somewhat above the upper end of the previously tacked piling member. The piling members typically have tongue and groove or other endwise slidable interlocking means extending along the full length of their side edges so that the piling members are securely interlocked together. The piling members may be moved longitudinally relative to one another. With the tongue and groove interlocked means of the previously tacked and the next piling member in sliding engagement with one another, the next piling member is lowered by the crane and is also tacked into the earth. Additional piling members are added to the cell following the form of the template so as to accurately position each of the piling members. Then, the tacked piling members are fully driven into the earth until the entire cofferdam cell is formed. After the shoring walls of the cofferdam cell are complete, the template is removed from the interior of the cell and, in some instances, the interior of the cell is filled with sand or other fill material so as to form a cofferdam. In other instances, the cell or shoring structure is used as a retaining wall and earth and water are removed from within the cell.
While a sheet piling cofferdam or other shoring structure may only be a temporary structure, the size and cost of constructing large cofferdams is immense. For example, in constructing a large dam and barge lock project in a river, a cellular piling cofferdam, a portion of which is shown in FIG. 1 of the drawings of the instant specification, may require 45 or more cells, each of which is about 65 feet (19.8 m.) in diameter and each containing approximately 165 sheet piling members, each of which is about 95 feet (28.9 m.) long with each of the piling members weighing approximately one and a half tons (1360 .sup.k g).
Because the cells of a cofferdam project are often interconnected, it is generally necessary to construct each of the cells consecutively one after the other. Thus, only one cell at a time may be constructed. Conventionally, the piling members are manually interconnected by a workman, sometimes referred to as a staber, or a pile monkey, positioned on top of the last-tacked piling member. The staber usually stands in removable metal stirrups applied to the top edge of the last-tacked piling member and he straddles the last-tacked piling member. The staber then manually guides the next piling member which is to be interconnected with the previously tacked piling members while the next piling member is supported overhead by a hoist or crane. Oftentimes, the staber must be located some 60-90 feet above the level of the ground (or water) while he is guiding the piling members into interlocking engagement. As previously mentioned, the next piling member to be interlocked is hoisted lengthwise by a crane so that its bottom edge is above the level of the last partially tacked piling member. While the next piling member is so hoisted by the crane, the staber must manually grasp the next piling member, turn it to correctly orient the interconnecting means along the edges of the piling members, and instruct the crane operator (usually by hand signals) how to lift, lower, or laterally move the hoisted piling member so that it can be guided into interlocking relation with the previously tacked piling member. However, due to the extreme length of the hoisted piling member, to the lack of a good working position as the staber straddles the upper edge of the previously tacked piling members while standing in the stirrups, to the great weight (and hence inertia) of the suspended piling member, and due to any wind that may be blowing, the staber's job of interconnecting the piling members is difficult, time consuming, and dangerous. If, upon sliding the interconnected piling members relative to one another, the piling members hang up, it is sometimes necessary for the staber to be lowered on a crane hook to the elevation to the level where the piling members are hung up in an effort to free the member. Of course, the lowering of the staber on the crane hook may, in some instances, be hazardous.
Because the job of interconnecting the piling members is dependent on ideal weather conditions, the sticking of the piling members cannot safely be carried out on windy days, even though the weather would be perfectly acceptable for other construction work. Thus, cofferdam construction jobs may be even more adversely affected by weather conditions than other types of construction. Accordingly, the cost of such cofferdam construction jobs are exceedingly difficult to accurately estimate and schedules for the completion of the cofferdam construction are difficult to meet.
As heretofore mentioned, the staber is supported on the upper edges of the previously tacked piling member some 60-90 feet above the level of the ground or the water. The staber is supported by removable stirrups engageable with the upper edges of the previously tacked piling members. As the adjacent piling members are interconnected and tacked, the staber must move the stirrups from one piling member to the next piling member. While these stirrups are, in effect, a safety support for the staber, they do not provide a stable and secure work platform. With the staber's legs straddling the ends of the tacked piling members, it is sometimes difficult for the staber to exert sufficient force on the hoisted piling member so as to jockey it into position for alignment with the interconnecting means. Also, in some instances, it is necessary for the staber to reach out for the piling member being hoisted. The stirrups do not permit the staber to move appreciable distances away from the stirrups and overreaching can cause the staber to lose his footing or balance. Additionally, the staber must, in many cases, ride on the hook of the crane so as to be lifted to or plucked from his tacking position on top the last-tacked piling members. This practice of riding the crane hook is sometimes dangerous. Still further, some staber's find it uncomfortable to remain standing in the stirrups or to sit on the relatively narrow upper edges of the previously tacked sheet piling members for any length of time. Thus, oftentimes the staber will need to be lifted down for a rest period and this even further impedes or slows down the positioning of additional piling members.
In an effort to provide a better work station for the staber, cofferdam contractors have utilized a wheel mounted hydraulic lift incorporating a telescopic boom with a workman support gasket thereon. These work supports are sometimes called "cherry picker" lifts. While these wheel mounted lifts did result in a more satisfactory support for the workman, they require that a special support platform be provided on the inside of the shoring structure, or that the wheel mounted lift be supported on the ground within the walls of the cellular shoring structure being constructed or on a barge.
In an effort to eliminate many of the problems and dangers of positioning a workman on the top of the previously tacked piling members, a variety of piling guides have been proposed, but, in general, these prior art piling guides have not met with widespread commercial acceptance. Certain of these piling guides are utilized by attaching the guide to the free side of a tacked piling member a few feet above the level of the ground. Then, the next piling member is lifted vertically and swung into place so as to be generally alongside of the previously tacked piling member and so that its lower edge is at the approximate elevation of the guide attached to the previously tacked piling member. Then, the next piling member is secured to the guide and the next piling member together with the guide is hoisted to a level until the guide is at the upper end of the last-tacked piling member and such that the bottom end of the next piling member is positioned somewhat above the upper edge of the last-tacked piling member. With the piling members in this position, a workman on the ground pulls a lanyard so as to actuate the guide and to move the hoisted piling member laterally thereby to axially align the interlocking means of the hoisted piling member with the previously tacked piling member. The crane operator then lowers the hoisted piling member and the interlocking means of the piling members are then endwise threadably engaged thus permitting the hoisted piling member to be lowered and to be tacked into the earth. When the next piling member is lowered down to a convenient working height, a workman on the ground then removes the guide and the next piling member is partially driven or tacked into the ground.
The above-described prior art piling guides have been intended primarily for the purpose of eliminating the necessity of a staber positioned on the top of the previously tacked piling members. However, in actual practice, difficulties have been encountered in making threading engagement between the interlocking means of the piling members. For example, the crane hoisting the next piling member may be supported on a floating barge and wave action may cause the crane and the hoisted pile to overrun or overshoot axial alignment thus making the threading difficult. Also, in driving piles, pile members of different lengths are sometimes used. After the different length pile members are tacked, shorter lengths of pile are added to make all piles the same height. However, these pile threaders cannot be used in aligning these shorter, fill-in piles. Still further, others of these pile threading devices are complicated pnuematic or hydraulic units of extreme complexity and weight.
Reference may be made to such U.S. patents to the following disclosing prior art sheet piling alignment and guide systems and sheet piling alignment apparatus in the same general field as the present invention: U.S. Pat. Nos. 2,161,428, 2,583,928, 2,833,119, 2,968,931, 3,688,509, 4,028,901, 4,083,192, 4,172,681 and 4,189,256.